At execution time, there are only three valid AMODE/RMODE combinations:
- AMODE 24, RMODE 24, which is the default
- AMODE 31, RMODE 24
- AMODE 31, RMODE ANY
The ATTACH, ATTACHX, LINK, LINKX, XCTL, and XCTLX macros give the
invoked module control in the AMODE previously specified. However,
specifying a particular AMODE does not guarantee that a module that
gets control by other means will receive control in that AMODE. For
example, an AMODE 24 module can issue a BALR to an AMODE 31, RMODE
24 module. The AMODE 31 module will get control in 24-bit addressing
mode.
Figure 1. AMODE and RMODE Combinations
- 1.
- This combination is invalid because an AMODE 24 module cannot reside above 16 megabytes.
- 2.
- This is a valid combination in that the assembler, linkage editor, and loader accept it from all sources. However, the combination is not used at execution time. Specifying ANY is a way of deferring a decision about the actual AMODE until the last possible moment before execution. At execution time, however, the module must execute in either 24-bit or 31-bit addressing mode.
- 3.
- The attributes AMODE ANY/RMODE ANY take on a special meaning
when used together. (This meaning might seem to disagree with the
meaning of either taken alone.) A module with the AMODE ANY/RMODE
ANY attributes will execute on either an MVS/370 or a system that
uses 31-bit addressing if the module is designed to:
- Use no facilities that are unique.
- Execute entirely in 31-bit addressing mode on a system that uses 31-bit addressing and return control to its caller in 31-bit addressing mode. (The AMODE could be different from invocation to invocation.)
- Execute entirely in 24-bit addressing mode on an MVS/370 system.
The linkage editor and loader accept this combination from the object module or load module but not from the PARM field of the linkage editor EXEC statement or the linkage editor MODE control statement. The linkage editor converts AMODE ANY/RMODE ANY to AMODE 31/RMODE ANY.